Applied Research Of Hybrid Energy Storage System In Grid Including Wind Farm

Thermal power and hydropower is mainly utilized in China Currently electricity supply. The power energy structure is extremely unreasonable on account of the small scale of wind power and photovoltaic. For this reason, the development of new energy power generation is put forward and the policies which comprehensively utilize renewable energy are encouraged in our country. The reasonable and effective use of renewable energy can solve the current energy crisis, optimize energy structure realize the urgent task of the sustainable development of energy and is of important strategic significance. Wind power is the most mature technology of power generation in renewable energy and wind power integration is the most effective way in the large-scale development and utilization of wind power. After wind power grid connection, there are many negative influences on power system operation and control due to the uncertainty and volatility of wind power. In this paper, the hybrid energy storage technology in wind power system which is used to solve the impact of wind power grid connected is in-depth analyzed and researched.Mathematical models of the voltage source dual-PWM converter in the three phases static coordinates and two phases synchronously rotating coordinates are established based on the analysis of the model of wind speed, wind turbine, converter. And on this basis the vector control strategy of DFIG is put forward, in which the rotor current control strategy based stator flux oriented is adopted in the rotor-side converter (RSC), the stator voltage oriented control strategy is adopted in the grid-side converter (GSC). Then the control performance got by adopting the control strategy in the rotor side and grid side converter is verified in the simulation.The energy storage properties of super capacitor and battery are analyzed, and on the basis of it their respective model are established. Mathematical model of Hybrid Energy Storage System (HESS) consisting of super capacitor through DC/DC converter and battery in parallel is established. The structure characteristics and operation mechanism of HESS are analyzed theoretically. The high power density, high energy density, long life and other characteristics possessed in the HESS are verified through simulation and experiment.The transient characteristic of DFIG is researched when symmetric fault or asymmetric fault takes place in power grid and crowbar protect is simultaneously activated. The LVRT control strategy of DFIG is proposes. The influence of crowbar protection resistance on rotor current and dc voltage of converter is analyzed. The selecting principle of rotor crowbar resistance is given. Influence of rotor crowbar protection on transient characteristic of DFIG in different crowbar resistance, different voltage drop depth and different crowbar protection engaged time is analysed through simulation.Aiming at the condition that the grid fault leads to different voltage drop, different protection strategies are adopted in the wind turbine and the converter. Low voltage ride through capability of DFIG is enhanced by improving the rotor side converter control strategy in litter voltage drop and by super capacitor combined with rotor crowbar protection in the deep voltage drop.Considering hybrid energy storage system used to smoothing power fluctuations, mathematical model of micro-grid operation optimization is established, in which aiming at the micro-grid operation cost minimum, the objective functions include the fuel cost, Sewage punishment fee and operation maintenance cost, etc. In the optimization examples the improved differential evolution algorithm is adopted to optimize the objective function. Numerical example results demonstrate the feasibility and effectiveness of the proposed model.Multi-objective optimization scheduling model is established including the generating cost of wind turbines and allocation cost of energy storage device capacity in this paper. Multi-optimization optimization scheduling model is solved by improved differential evolution algorithm. IEEE 30-bus system numerical example containing wind turbines and hybrid energy storage systems has been optimazed by improved differential evolution algorithm. Numerical example results demonstrated that the power fluctuation of wind farm gets improved significantly after optimization the influence of the wind stochastic characteristics on stable operation of power system is weakened and the schedulable of wind farms is improved.